Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$208.67	12.387%	$234.518	$234.52	$234.50	$234.50
Purchase #2	$123.43	7.673%	$132.9008	$132.90	$132.90	$132.90
Purchase #3	$129.42	13.351%	$146.6989	$146.70	$146.70	$146.70
Purchase #4	$245.97	3.403%	$254.3404	$254.34	$254.35	$254.30
Purchase #5	$59.54	13.345%	$67.4856	$67.49	$67.50	$67.50
Purchase #6	$61.28	5.492%	$64.6455	$64.65	$64.65	$64.60
Purchase #7	$127.47	13.787%	$145.0443	$145.04	$145.05	$145.00
7 purchase totals =	$955.78		$1,045.6335	$1,045.64	$1,045.65	$1,045.50